The present invention relates to the Dry Vacuum/Pressure Process for impregnating parts and components with liquid impregnants.
In the Dry Vacuum/Pressure Impregnation Process, a part to be impregnated is placed in an impregnation chamber where a vacuum is drawn on the part. A liquid impregnant such as methyl methacrylate is then charged into the chamber, after which the vacuum is released to allow liquid impregnant into the part's micropores. The chamber is then pressurized to drive additional sealant into the micropores, after which the pressure is returned to atmospheric and the liquid impregnant withdrawn from the chamber to complete the impregnation process. After withdrawal from the chamber, excess sealant is removed from the part, and the part is then washed and heated to cure the sealant.
U.S. Pat. No. 4,479,986 to Juday describes technology for carrying out the Dry Vacuum/Pressure Impregnation Process in which the liquid impregnant is maintained in the impregnation chamber at all times, i.e., the liquid impregnant is not charged into and then withdrawn from the impregnation chamber during each impregnation cycle. A carrier is provided inside the impregnation chamber to support the parts being impregnated above the liquid impregnant while the vacuum is being drawn and then to lower the parts into the liquid impregnant for release of the vacuum and subsequent pressurization. One advantage of this approach, according to Juday, is shorter cycle times, since the time needed to charge and then discharge liquid impregnant is avoided.
However, the Juday technology is not used commercially, which is presumably due to the complex system needed to load, move and unload the parts into, within and out of the impregnation chamber. Thus, the Juday system uses a complicated transport assembly to lower and raise the parts to be impregnated into and out of the open top of Juday's impregnation chamber as well as to different positions inside this chamber during impregnation. In addition, this transport assembly also lowers and raises the cover used to close and seal the impregnation chamber. In addition, this transport assembly also spins the parts inside the chamber, since centrifuging the parts inside the impregnation chamber is an important feature of the Juday system. All of this complexity makes the Juday apparatus impractical from a commercial stand point.
For example, it is important for the automatic, trouble free operation of the Juday system that the parts in Juday's impregnation chamber accurately register with the conveyors and transport equipment used for loading and unloading these parts. In addition, it is also important that the cover which closes Juday's impregnation chamber accurately register with the open top of this chamber to insure a pressure-tight seal. Unfortunately, the many large, cumbersome, vertically-moving, structural elements that are part of Juday's transport assembly make accurate registration virtually impossible over time, because these elements are prone to wearing out because of their size, shape, weight, and complex movements.
Accordingly, it is an object of the present invention to provide new technology for impregnating parts with liquid impregnant by the Dry Vacuum/Pressure Impregnation Process using apparatus which avoids the large and cumbersome vertically moving structural elements of Juday's system while at the same time still allows the liquid impregnant to remain in the impregnation chamber for increased cycle time efficiency.